1. Field of the Invention
The present invention relates to a shield for protecting spacecraft structures from impact with hypervelocity objects having densities on the average of 4.0 g/cm.sup.3 or more.
2. Description of Related Art
During the early years of space exploration, the principal danger to spacecraft in the low earth orbit environment consisted of high velocity (approximately 20 km/sec), small (approximately 10.sup.-6 g), low density (approximately 0.6 g/cm.sup.3) micrometeoroids impacting the spacecraft. To combat this threat, a shield was designed known as the Whipple shield, which consists of two aluminum components. These components have generally been referred to as the "bumper" and the "base armor" with the base armor being the last component of protection to the spacecraft. The Whipple shield also includes a space between the two components. By using two components with a space between them, less mass per unit area is required for the same protection as provided by a single solid aluminum shield. A projectile impacting the bumper at hypervelocity fragments into a debris cloud. This debris cloud will spread out while it travels through the space between the bumper and the base armor, and thus will impact the base armor over a wider area. This dispersed impact decreases the probability of penetration of the base armor protecting vulnerable components of the spacecraft.
Over the past 30 years, there has been an increase in the amount of orbital debris from man-made sources. In addition to the increase in the amount of debris, the newer debris have been estimated to have dramatically increased in density to an average of 4.5 g/cm.sup.3 or more. Hypervelocity impact experiments have shown that the current Whipple shields are not adequate to protect against these new larger, higher density debris. Accordingly, a shield that will provide adequate protection without drastically increasing the shielding mass would be advantageous because of the costs associated with launching heavy payloads.